// Helper function for the normalize() mixin.
@function _normalize-include($section, $exclude: null) {
  // Initialize the global variables needed by this function.
  @if not global_variable_exists(_normalize-include) {
    $_normalize-include: () !global;
    $_normalize-exclude: () !global;
  }
  // Since we are given 2 parameters, set the global variables.
  @if $exclude != null {
    $include: $section;
    // Sass doesn't have static variables, so the work-around is to stuff these
    // values into global variables so we can access them in future calls.
    $_normalize-include: if(type-of($include) == 'list', $include, ($include)) !global;
    $_normalize-exclude: if(type-of($exclude) == 'list', $exclude, ($exclude)) !global;
    @return true;
  }

  // Check if $section is in the $include list.
  @if index($_normalize-include, $section) {
    @return true;
  }
  // If $include is set to (all), make sure $section is not in $exclude.
  @else if not index($_normalize-exclude, $section) and index($_normalize-include, all) {
    @return true;
  }
  @return false;
}

@mixin normalize($include: (all), $exclude: ()) {
  // Initialize the helper function by passing it this mixin's parameters.
  $init: _normalize-include($include, $exclude);

  // If we've customized any font variables, we'll need extra properties.
  @if $base-line-height != 24px
    or $base-unit != 'em'
    or $h2-font-size != 1.5  * $base-font-size
    or $h3-font-size != 1.17 * $base-font-size
    or $h4-font-size != 1    * $base-font-size
    or $h5-font-size != 0.83 * $base-font-size
    or $h6-font-size != 0.67 * $base-font-size {
    $normalize-vertical-rhythm: true !global;
  }

  /*! normalize-scss | MIT/GPLv2 License | bit.ly/normalize-scss */

  @if _normalize-include(document) {
    /* Document
       ========================================================================== */

    /**
     * 1. Correct the line height in all browsers.
     * 2. Prevent adjustments of font size after orientation changes in
     *    IE on Windows Phone and in iOS.
     */

    html {
      @if $base-font-family {
        /* Change the default font family in all browsers (opinionated). */
        font-family: $base-font-family;
      }
      @if $base-font-size != 16px or $normalize-vertical-rhythm {
        // Correct old browser bug that prevented accessible resizing of text
        // when root font-size is set with px or em.
        font-size: ($base-font-size / 16px) * 100%;
      }
      @if $normalize-vertical-rhythm {
        line-height: ($base-line-height / $base-font-size) * 1em; /* 1 */
      }
      @else {
        line-height: 1.15; /* 1 */
      }
      -ms-text-size-adjust: 100%; /* 2 */
      -webkit-text-size-adjust: 100%; /* 2 */
    }
  }

  @if _normalize-include(sections) {
    /* Sections
       ========================================================================== */

    /**
     * Remove the margin in all browsers (opinionated).
     */

    body {
      margin: 0;
    }

    /**
     * Add the correct display in IE 9-.
     */

    article,
    aside,
    footer,
    header,
    nav,
    section {
      display: block;
    }

    /**
     * Correct the font size and margin on `h1` elements within `section` and
     * `article` contexts in Chrome, Firefox, and Safari.
     */

    h1 {
      @include normalize-font-size($h1-font-size);
      @if $normalize-vertical-rhythm {
        @include normalize-line-height($h1-font-size);
      }

      @if $normalize-vertical-rhythm {
        /* Set 1 unit of vertical rhythm on the top and bottom margins. */
        @include normalize-margin(1 0, $h1-font-size);
      }
      @else {
        margin: 0.67em 0;
      }
    }

    @if $normalize-vertical-rhythm {
      h2 {
        @include normalize-font-size($h2-font-size);
        @include normalize-line-height($h2-font-size);
        @include normalize-margin(1 0, $h2-font-size);
      }

      h3 {
        @include normalize-font-size($h3-font-size);
        @include normalize-line-height($h3-font-size);
        @include normalize-margin(1 0, $h3-font-size);
      }

      h4 {
        @include normalize-font-size($h4-font-size);
        @include normalize-line-height($h4-font-size);
        @include normalize-margin(1 0, $h4-font-size);
      }

      h5 {
        @include normalize-font-size($h5-font-size);
        @include normalize-line-height($h5-font-size);
        @include normalize-margin(1 0, $h5-font-size);
      }

      h6 {
        @include normalize-font-size($h6-font-size);
        @include normalize-line-height($h6-font-size);
        @include normalize-margin(1 0, $h6-font-size);
      }
    }
  }

  @if _normalize-include(grouping) {
    /* Grouping content
       ========================================================================== */

    @if $normalize-vertical-rhythm {
      /**
       * Set 1 unit of vertical rhythm on the top and bottom margin.
       */

      blockquote {
        @include normalize-margin(1 $indent-amount);
      }

      dl,
      ol,
      ul {
        @include normalize-margin(1 0);
      }

      /**
       * Turn off margins on nested lists.
       */

      ol,
      ul {
        ol,
        ul {
          margin: 0;
        }
      }

      dd {
        margin: 0 0 0 $indent-amount;
      }

      ol,
      ul {
        padding: 0 0 0 $indent-amount;
      }
    }

    /**
     * Add the correct display in IE 9-.
     */

    figcaption,
    figure {
      display: block;
    }

    /**
     * Add the correct margin in IE 8.
     */

    figure {
      @if $normalize-vertical-rhythm {
        @include normalize-margin(1 $indent-amount);
      }
      @else {
        margin: 1em $indent-amount;
      }
    }

    /**
     * 1. Add the correct box sizing in Firefox.
     * 2. Show the overflow in Edge and IE.
     */

    hr {
      box-sizing: content-box; /* 1 */
      height: 0; /* 1 */
      overflow: visible; /* 2 */
    }

    /**
     * Add the correct display in IE.
     */

    main {
      display: block;
    }

    @if $normalize-vertical-rhythm {
      /**
       * Set 1 unit of vertical rhythm on the top and bottom margin.
       */

      p,
      pre {
        @include normalize-margin(1 0);
      }
    }

    /**
     * 1. Correct the inheritance and scaling of font size in all browsers.
     * 2. Correct the odd `em` font sizing in all browsers.
     */

    pre {
      font-family: monospace, monospace; /* 1 */
      font-size: 1em; /* 2 */
    }
  }

  @if _normalize-include(links) {
    /* Links
       ========================================================================== */

    /**
     * 1. Remove the gray background on active links in IE 10.
     * 2. Remove gaps in links underline in iOS 8+ and Safari 8+.
     */

    a {
      background-color: transparent; /* 1 */
      -webkit-text-decoration-skip: objects; /* 2 */
    }
  }

  @if _normalize-include(text) {
    /* Text-level semantics
       ========================================================================== */

    /**
     * 1. Remove the bottom border in Chrome 57- and Firefox 39-.
     * 2. Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.
     */

    abbr[title] {
      border-bottom: none; /* 1 */
      text-decoration: underline; /* 2 */
      text-decoration: underline dotted; /* 2 */
    }

    /**
     * Prevent the duplicate application of `bolder` by the next rule in Safari 6.
     */

    b,
    strong {
      font-weight: inherit;
    }

    /**
     * Add the correct font weight in Chrome, Edge, and Safari.
     */

    b,
    strong {
      font-weight: bolder;
    }

    /**
     * 1. Correct the inheritance and scaling of font size in all browsers.
     * 2. Correct the odd `em` font sizing in all browsers.
     */

    code,
    kbd,
    samp {
      font-family: monospace, monospace; /* 1 */
      font-size: 1em; /* 2 */
    }

    /**
     * Add the correct font style in Android 4.3-.
     */

    dfn {
      font-style: italic;
    }

    /**
     * Add the correct background and color in IE 9-.
     */

    mark {
      background-color: #ff0;
      color: #000;
    }

    /**
     * Add the correct font size in all browsers.
     */

    small {
      font-size: 80%;
    }

    /**
     * Prevent `sub` and `sup` elements from affecting the line height in
     * all browsers.
     */

    sub,
    sup {
      font-size: 75%;
      line-height: 0;
      position: relative;
      vertical-align: baseline;
    }

    sub {
      bottom: -0.25em;
    }

    sup {
      top: -0.5em;
    }
  }

  @if _normalize-include(embedded) {
    /* Embedded content
       ========================================================================== */

    /**
     * Add the correct display in IE 9-.
     */

    audio,
    video {
      display: inline-block;
    }

    /**
     * Add the correct display in iOS 4-7.
     */

    audio:not([controls]) {
      display: none;
      height: 0;
    }

    /**
     * Remove the border on images inside links in IE 10-.
     */

    img {
      border-style: none;
    }

    /**
     * Hide the overflow in IE.
     */

    svg:not(:root) {
      overflow: hidden;
    }
  }

  @if _normalize-include(forms) {
    /* Forms
       ========================================================================== */

    /**
     * 1. Change the font styles in all browsers (opinionated).
     * 2. Remove the margin in Firefox and Safari.
     */

    button,
    input,
    optgroup,
    select,
    textarea {
      font-family: if($base-font-family, $base-font-family, sans-serif); /* 1 */
      font-size: 100%; /* 1 */
      @if $normalize-vertical-rhythm {
        line-height: ($base-line-height / $base-font-size) * 1em; /* 1 */
      }
      @else {
        line-height: 1.15; /* 1 */
      }
      margin: 0; /* 2 */
    }

    /**
     * Show the overflow in IE.
     */

    button {
      overflow: visible;
    }

    /**
     * Remove the inheritance of text transform in Edge, Firefox, and IE.
     * 1. Remove the inheritance of text transform in Firefox.
     */

    button,
    select { /* 1 */
      text-transform: none;
    }

    /**
     * 1. Prevent a WebKit bug where (2) destroys native `audio` and `video`
     *    controls in Android 4.
     * 2. Correct the inability to style clickable types in iOS and Safari.
     */

    button,
    html [type="button"], /* 1 */
    [type="reset"],
    [type="submit"] {
      -webkit-appearance: button; /* 2 */
    }

    button,
    [type="button"],
    [type="reset"],
    [type="submit"] {

      /**
       * Remove the inner border and padding in Firefox.
       */

      &::-moz-focus-inner {
        border-style: none;
        padding: 0;
      }

      /**
       * Restore the focus styles unset by the previous rule.
       */

      &:-moz-focusring {
        outline: 1px dotted ButtonText;
      }
    }

    /**
     * Show the overflow in Edge.
     */

    input {
      overflow: visible;
    }

    /**
     * 1. Add the correct box sizing in IE 10-.
     * 2. Remove the padding in IE 10-.
     */

    [type="checkbox"],
    [type="radio"] {
      box-sizing: border-box; /* 1 */
      padding: 0; /* 2 */
    }

    /**
     * Correct the cursor style of increment and decrement buttons in Chrome.
     */

    [type="number"]::-webkit-inner-spin-button,
    [type="number"]::-webkit-outer-spin-button {
      height: auto;
    }

    /**
     * 1. Correct the odd appearance in Chrome and Safari.
     * 2. Correct the outline style in Safari.
     */

    [type="search"] {
      -webkit-appearance: textfield; /* 1 */
      outline-offset: -2px; /* 2 */

      /**
       * Remove the inner padding and cancel buttons in Chrome and Safari on macOS.
       */

      &::-webkit-search-cancel-button,
      &::-webkit-search-decoration {
        -webkit-appearance: none;
      }
    }

    /**
     * 1. Correct the inability to style clickable types in iOS and Safari.
     * 2. Change font properties to `inherit` in Safari.
     */

    ::-webkit-file-upload-button {
      -webkit-appearance: button; /* 1 */
      font: inherit; /* 2 */
    }

    /**
     * Correct the padding in Firefox.
     */

    fieldset {
      padding: 0.35em 0.75em 0.625em;
    }

    /**
     * 1. Correct the text wrapping in Edge and IE.
     * 2. Correct the color inheritance from `fieldset` elements in IE.
     * 3. Remove the padding so developers are not caught out when they zero out
     *    `fieldset` elements in all browsers.
     */

    legend {
      box-sizing: border-box; /* 1 */
      display: table; /* 1 */
      max-width: 100%; /* 1 */
      padding: 0; /* 3 */
      color: inherit; /* 2 */
      white-space: normal; /* 1 */
    }

    /**
     * 1. Add the correct display in IE 9-.
     * 2. Add the correct vertical alignment in Chrome, Firefox, and Opera.
     */

    progress {
      display: inline-block; /* 1 */
      vertical-align: baseline; /* 2 */
    }

    /**
     * Remove the default vertical scrollbar in IE.
     */

    textarea {
      overflow: auto;
    }
  }

  @if _normalize-include(interactive) {
    /* Interactive
       ========================================================================== */

    /*
     * Add the correct display in Edge, IE, and Firefox.
     */

    details {
      display: block;
    }

    /*
     * Add the correct display in all browsers.
     */

    summary {
      display: list-item;
    }

    /*
     * Add the correct display in IE 9-.
     */

    menu {
      display: block;

      @if $normalize-vertical-rhythm {
        /*
         * 1. Set 1 unit of vertical rhythm on the top and bottom margin.
         * 2. Set consistent space for the list style image.
         */

        @include normalize-margin(1 0); /* 1 */
        padding: 0 0 0 $indent-amount; /* 2 */

        /**
         * Turn off margins on nested lists.
         */

        menu &,
        ol &,
        ul & {
          margin: 0;
        }
      }
    }
  }

  @if _normalize-include(scripting) {
    /* Scripting
       ========================================================================== */

    /**
     * Add the correct display in IE 9-.
     */

    canvas {
      display: inline-block;
    }

    /**
     * Add the correct display in IE.
     */

    template {
      display: none;
    }
  }

  @if _normalize-include(hidden) {
    /* Hidden
       ========================================================================== */

    /**
     * Add the correct display in IE 10-.
     */

    [hidden] {
      display: none;
    }
  }
}
